org.dspace.content.crosswalk

Class PREMISCrosswalk

java.lang.Object

org.dspace.content.crosswalk.PREMISCrosswalk

All Implemented Interfaces:

DisseminationCrosswalk, IngestionCrosswalk

public class PREMISCrosswalk
extends Object
implements IngestionCrosswalk, DisseminationCrosswalk

PREMIS Crosswalk

Translate between DSpace Bitstream properties and PREMIS metadata format (see http://www.oclc.org/research/projects/pmwg/ for details). This is intended to implement the requirements of the DSpace METS SIP specification for both ingest and dissemination.

Version:

$Revision$

Author:

Larry Stone

Field Summary

Fields inherited from interface org.dspace.content.crosswalk.DisseminationCrosswalk

XSI_NS

Constructor Summary

Constructors

Constructor and Description
PREMISCrosswalk()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	canDisseminate(DSpaceObject dso) Predicate: Can this disseminator crosswalk the given object.
org.jdom.Element	disseminateElement(DSpaceObject dso) Execute crosswalk, returning one XML root element as a JDOM Element object.
List<org.jdom.Element>	disseminateList(DSpaceObject dso) Execute crosswalk, returning List of XML elements.
org.jdom.Namespace[]	getNamespaces() Get XML namespaces of the elements this crosswalk may return.
String	getSchemaLocation() Get the XML Schema location(s) of the target metadata format.
void	ingest(Context context, DSpaceObject dso, org.jdom.Element root) Crosswalk metadata from external XML representation to DSpace internal representations.
void	ingest(Context context, DSpaceObject dso, List<org.jdom.Element> ml) Crosswalk metadata from external XML representation to DSpace internal representations.
boolean	preferList() Predicate: Does this disseminator prefer to return a list of Elements, rather than a single root Element?

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PREMISCrosswalk

public PREMISCrosswalk()

Method Detail

ingest

public void ingest(Context context,
          DSpaceObject dso,
          org.jdom.Element root)
            throws CrosswalkException,
                   IOException,
                   SQLException,
                   AuthorizeException

Description copied from interface: IngestionCrosswalk

Crosswalk metadata from external XML representation to DSpace internal representations. This version accepts a single "root" element of the XML metadata.

It is otherwise just like the List form of ingest() above.

Specified by:

ingest in interface IngestionCrosswalk

Parameters:

context - DSpace context.

dso - DSpace Object (usually an Item) to which new metadata gets attached.

root - root Element of metadata document.

Throws:

CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.

CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk into this kind of DSpace object.

MetadataValidationException - (CrosswalkException) metadata format was not acceptable or missing required elements.

IOException - I/O failure in services this calls

SQLException - Database failure in services this calls

AuthorizeException - current user not authorized for this operation.

CrosswalkException

ingest

public void ingest(Context context,
          DSpaceObject dso,
          List<org.jdom.Element> ml)
            throws CrosswalkException,
                   IOException,
                   SQLException,
                   AuthorizeException

Description copied from interface: IngestionCrosswalk

Crosswalk metadata from external XML representation to DSpace internal representations. This version accepts metadata as a List of JDOM XML elements. It interprets the contents of each element and adds the appropriate values to the DSpace Object's internal metadata represenation.

Note that this method may be called several times for the same target Item, if the metadata comes as several lists of elements, so it should not add fixed metadata values on each or they may appear multiples times.

NOTE:
Most XML metadata standards (e.g. MODS) are defined as a "root" element which contains a sequence of "fields" that have the descriptive information. Some metadata containers have a "disembodied" list of fields, rather than the root element, so this ingest method is intended to accept that bare list of fields. However, it must also accept a list containing only the "root" element for the metadata structure (e.g. the "mods:mods" wrapper in a MODS expression) as a member of the list. It can handle this case by calling the single-element version of ingest() on the "root" element.

Some callers of the crosswalk plugin may not be careful about (or capable of) choosing whether the list or element version should be called.

Specified by:

ingest in interface IngestionCrosswalk

Parameters:

context - DSpace context.

dso - DSpace Object (Item, Bitstream, etc) to which new metadata gets attached.

ml - List of XML Elements of metadata

Throws:

CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.

CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk into this kind of DSpace object.

MetadataValidationException - (CrosswalkException) metadata format was not acceptable or missing required elements.

IOException - I/O failure in services this calls

SQLException - Database failure in services this calls

AuthorizeException - current user not authorized for this operation.

CrosswalkException

getNamespaces

public org.jdom.Namespace[] getNamespaces()

Description copied from interface: DisseminationCrosswalk

Get XML namespaces of the elements this crosswalk may return. Returns the XML namespaces (as JDOM objects) of the root element.

Specified by:

getNamespaces in interface DisseminationCrosswalk

Returns:

array of namespaces, which may be empty.

getSchemaLocation

public String getSchemaLocation()

Description copied from interface: DisseminationCrosswalk

Get the XML Schema location(s) of the target metadata format. Returns the string value of the xsi:schemaLocation attribute that should be applied to the generated XML.

It may return the empty string if no schema is known, but crosswalk authors are strongly encouraged to implement this call so their output XML can be validated correctly.

Specified by:

getSchemaLocation in interface DisseminationCrosswalk

Returns:

SchemaLocation string, including URI namespace, followed by whitespace and URI of XML schema document, or empty string if unknown.

canDisseminate

public boolean canDisseminate(DSpaceObject dso)

Description copied from interface: DisseminationCrosswalk

Predicate: Can this disseminator crosswalk the given object. Needed by OAI-PMH server implementation.

Specified by:

canDisseminate in interface DisseminationCrosswalk

Parameters:

dso - dspace object, e.g. an Item.

Returns:

true when disseminator is capable of producing metadata.

disseminateElement

public org.jdom.Element disseminateElement(DSpaceObject dso)
                                    throws CrosswalkException,
                                           IOException,
                                           SQLException,
                                           AuthorizeException

Description copied from interface: DisseminationCrosswalk

Execute crosswalk, returning one XML root element as a JDOM Element object. This is typically the root element of a document.

Specified by:

disseminateElement in interface DisseminationCrosswalk

Parameters:

dso - the DSpace Object whose metadata to export.

Returns:

root Element of the target metadata, never null

Throws:

CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.

CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk this kind of DSpace object.

IOException - I/O failure in services this calls

SQLException - Database failure in services this calls

AuthorizeException - current user not authorized for this operation.

CrosswalkException

disseminateList

public List<org.jdom.Element> disseminateList(DSpaceObject dso)
                                       throws CrosswalkException,
                                              IOException,
                                              SQLException,
                                              AuthorizeException

Description copied from interface: DisseminationCrosswalk

Execute crosswalk, returning List of XML elements. Returns a List of JDOM Element objects representing the XML produced by the crosswalk. This is typically called when a list of fields is desired, e.g. for embedding in a METS document xmlData field.

When there are no results, an empty list is returned, but never null.

Specified by:

disseminateList in interface DisseminationCrosswalk

Parameters:

dso - the DSpace Object whose metadata to export.

Returns:

results of crosswalk as list of XML elements.

Throws:

CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.

CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk this kind of DSpace object.

IOException - I/O failure in services this calls

SQLException - Database failure in services this calls

AuthorizeException - current user not authorized for this operation.

CrosswalkException

preferList

public boolean preferList()

Description copied from interface: DisseminationCrosswalk

Predicate: Does this disseminator prefer to return a list of Elements, rather than a single root Element?

Some metadata formats have an XML schema without a root element, for example, the Dublin Core and Qualified Dublin Core formats. This would be true for a crosswalk into QDC, since it would "prefer" to return a list, since any root element it has to produce would have to be part of a nonstandard schema. In most cases your implementation will want to return false

Specified by:

preferList in interface DisseminationCrosswalk

Returns:

true when disseminator prefers you call disseminateList().